You are Here: Home >< Maths

# *HELP* AS Maths Edexcel Trigonometry watch

1. Alright so I have this question and I’m completely stuck on it. I can’t seem to get my value of x to be = to what it wants in question part a. I used angles in a triangle to figure out the other angle which is 45 I then used sine rule and solved algebraically but it’s not working for me.

All help and solutions appreciated!

The diagram shows triangle ABC with AC=8x-3, BC=4x-1, angle ABC=120 degrees and angle ACB=15 degrees.

(a) Show that the exact value of x is 9+√6/20 (7 marks)
(b) Find the area of triangle ABC giving your answer to 2 decimal places
(3 marks)
4. (Original post by fabalas)
Use the sine rule:

Sin 120/(8x - 3) = sin 45/(4x - 1)

You should know exact values for sin 120 and sin 45.
5. (Original post by fabalas)
Alright so I have this question and I’m completely stuck on it. I can’t seem to get my value of x to be = to what it wants in question part a. I used angles in a triangle to figure out the other angle which is 45 I then used sine rule and solved algebraically but it’s not working for me.

All help and solutions appreciated!

The diagram shows triangle ABC with AC=8x-3, BC=4x-1, angle ABC=120 degrees and angle ACB=15 degrees.

(a) Show that the exact value of x is 9+√6/20 (7 marks)
(b) Find the area of triangle ABC giving your answer to 2 decimal places
(3 marks)
Did you get the equation to be

{2/sqrt(3)}(8x-3) = {sqrt(2)}(4x-1) ?

Solving this equation gives you the required value of x.
6. a) Sine rule. I'll work in terms of sin for you:

4x-1 / sin45 = 8x-3 / sin 120
--> 4x sin120 - sin120 = 8x sin45 - 3sin45
--> 4x sin120 - 8x sin45 = sin120 - 3sin45
--> x[4sin120 - 8sin45] = sin120 -3sin45

--> x = sin120 - 3sin45 / (4sin120-8sin45) = 9 + root 6 / 20, QED.

I want you to complete the steps I missed purposefully.
7. Thank you so much! That’s helped a lot!
8. where is this question from?
(Original post by fabalas)
Alright so I have this question and I’m completely stuck on it. I can’t seem to get my value of x to be = to what it wants in question part a. I used angles in a triangle to figure out the other angle which is 45 I then used sine rule and solved algebraically but it’s not working for me.

All help and solutions appreciated!

The diagram shows triangle ABC with AC=8x-3, BC=4x-1, angle ABC=120 degrees and angle ACB=15 degrees.

(a) Show that the exact value of x is 9+√6/20 (7 marks)
(b) Find the area of triangle ABC giving your answer to 2 decimal places
(3 marks)
9. (Original post by Revisionwithmae)
where is this question from?
It’s from the edexcel trig milestone, I had the question in the milestone test and had to complete improvements on it.

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: March 12, 2018
Today on TSR

How do you think you'll do?

### University open days

Wed, 25 Jul '18
2. University of Buckingham
Wed, 25 Jul '18
3. Bournemouth University
Wed, 1 Aug '18
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams